Erractic revving/Fuel Pumps
11-01-2017, 08:44 PM
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Year: 1990
Model: Cherokee(XJ)
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Erractic revving/Fuel Pumps
90 Cherokee XJ
4.0L
5-Speed
Howdy all.
I've a very noisy fuel pump/erratic revving and I was looking to replace it to possibly cut down on the noise and mayhaps solve my revving issue. I do have a high idling problem and have done the following to address it: cleaned TB [wasn't too dirty but did so anyways], replaced TB gasket [previous gasket was def brittle and worn out], cleaned IAC [again, like TB it wasn't too dirty but the O-ring was pinched in one section], ended up replacing the IAC [a few threads I'd read previously suggested the IAC being the cause of a high idle]. I will say, the idle starts high and then calms down [revs on days first start up, and follow on start ups, to 2k rpm then down to 750ish rpms] but occasionally the idle will hover between 250 and 500 rpms, almost bogging down with the first start of the day [I assume because of the cold engine]. As the day warms up, I usually see the normal rev to 2k then relax to 750...
Wondering if this is normal [the rev and relax as well as cold start fluctuation on the low end of the rpms] for Jeeps and if possibly the fuel pump being on its last legs is the cause for this erratic revving.
My next COAs, that I can think of, are one or all or a combo of the following: replacing the fuel pressure regulator, cleaning the fuel rail and injectors [as well as replacing the o-rings on the injectors], replacing/upgrading the injectors to multiport versions [pretty sure ive stock single ports].
Additionally, I've heard multiple people mention staying away from Delphi fuel pumps [Delphi being rebranded Airtek versions which have shoddy craftmanship. With Bosch and Carter seem to have the most positive feedback]. COULD the previous problems with Delphi pumps be caused by not also changing the fuel pressure regulator to a Delphi brand as well? As in the Delphi brand fuel pumps not "talking" well to non Delphi brand fuel pressure regulators? This last question is just a random thought...
I'm new to repairing cars and Jeeps in general, be gentle if my thinking is skewed, lol.
Thanks in advance ladies and gents.
4.0L
5-Speed
Howdy all.
I've a very noisy fuel pump/erratic revving and I was looking to replace it to possibly cut down on the noise and mayhaps solve my revving issue. I do have a high idling problem and have done the following to address it: cleaned TB [wasn't too dirty but did so anyways], replaced TB gasket [previous gasket was def brittle and worn out], cleaned IAC [again, like TB it wasn't too dirty but the O-ring was pinched in one section], ended up replacing the IAC [a few threads I'd read previously suggested the IAC being the cause of a high idle]. I will say, the idle starts high and then calms down [revs on days first start up, and follow on start ups, to 2k rpm then down to 750ish rpms] but occasionally the idle will hover between 250 and 500 rpms, almost bogging down with the first start of the day [I assume because of the cold engine]. As the day warms up, I usually see the normal rev to 2k then relax to 750...
Wondering if this is normal [the rev and relax as well as cold start fluctuation on the low end of the rpms] for Jeeps and if possibly the fuel pump being on its last legs is the cause for this erratic revving.
My next COAs, that I can think of, are one or all or a combo of the following: replacing the fuel pressure regulator, cleaning the fuel rail and injectors [as well as replacing the o-rings on the injectors], replacing/upgrading the injectors to multiport versions [pretty sure ive stock single ports].
Additionally, I've heard multiple people mention staying away from Delphi fuel pumps [Delphi being rebranded Airtek versions which have shoddy craftmanship. With Bosch and Carter seem to have the most positive feedback]. COULD the previous problems with Delphi pumps be caused by not also changing the fuel pressure regulator to a Delphi brand as well? As in the Delphi brand fuel pumps not "talking" well to non Delphi brand fuel pressure regulators? This last question is just a random thought...
I'm new to repairing cars and Jeeps in general, be gentle if my thinking is skewed, lol.
Thanks in advance ladies and gents.
11-01-2017, 10:04 PM
#2
CF Veteran
Welcome to the forum.
You need to fill out your profile so we know what jeep you are talking about.
That said high idle is often an intake vacuum leak. Check hoses fittings clamps,,throttle body bolts.. and intake gasket. Without your info we are shooting in the dark.
We like not to guess here so I recommend a fuel pressure test, scan for codes.
You need to fill out your profile so we know what jeep you are talking about.
That said high idle is often an intake vacuum leak. Check hoses fittings clamps,,throttle body bolts.. and intake gasket. Without your info we are shooting in the dark.
We like not to guess here so I recommend a fuel pressure test, scan for codes.
11-01-2017, 10:46 PM
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Welcome to the forum.
You need to fill out your profile so we know what jeep you are talking about.
That said high idle is often an intake vacuum leak. Check hoses fittings clamps,,throttle body bolts.. and intake gasket. Without your info we are shooting in the dark.
We like not to guess here so I recommend a fuel pressure test, scan for codes.
You need to fill out your profile so we know what jeep you are talking about.
That said high idle is often an intake vacuum leak. Check hoses fittings clamps,,throttle body bolts.. and intake gasket. Without your info we are shooting in the dark.
We like not to guess here so I recommend a fuel pressure test, scan for codes.
Hooked up the requested info, sorry about that.
The Vacuum Lines are on the list of things that definitely need replacing. They look simple enough to replace, is it strictly plug and play with installing a new vacuum harness?
11-02-2017, 07:00 AM
#4
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there is no such thing as a vacuum harness.
11-02-2017, 08:36 AM
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11-02-2017, 08:44 AM
#6
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Year: 1990
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Ok, Joshua. It's pretty obvious 97grand is NOT familiar with the Renix fuel injection system that you have.
Let's start over.
Most likely, the problem is your TPS.
That said, there are a few steps you should take before just replacing it.
Go to my website www.cruiser54.com and perform Tips 1,3,4, and 5. In order. The test results from Tip 5 are very important.
Report back and I'll get you through this.
Let's start over.
Most likely, the problem is your TPS.
That said, there are a few steps you should take before just replacing it.
Go to my website www.cruiser54.com and perform Tips 1,3,4, and 5. In order. The test results from Tip 5 are very important.
Report back and I'll get you through this.
11-02-2017, 08:54 AM
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Hey cruiser54.
I did slap a multimeter onto the wiring while the torx screws were loose on the TPS, got the voltage, did the math, and made sure the TPS was adjusted until it read 17%, then locked it down.
I replaced the rotar, distirbuter cap, spark plug wires,and spark plugs as well.
Cruiser, are the harnesses as simple as plug and play when replacing? They definitely need replacing...
Didnt go as in depth as your tips suggest, so ill jump on it and get back to you.
Oh, and thanks 97grand4.0. Hope I didnt come across as snarky, I appreciate the quick responses.
I did slap a multimeter onto the wiring while the torx screws were loose on the TPS, got the voltage, did the math, and made sure the TPS was adjusted until it read 17%, then locked it down.
I replaced the rotar, distirbuter cap, spark plug wires,and spark plugs as well.
Cruiser, are the harnesses as simple as plug and play when replacing? They definitely need replacing...
Didnt go as in depth as your tips suggest, so ill jump on it and get back to you.
Oh, and thanks 97grand4.0. Hope I didnt come across as snarky, I appreciate the quick responses.
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11-02-2017, 09:07 AM
#8
CF Veteran
Whoops! My bad. I have been wrong before and was wrong again. However I would still suspect a vacuum leak, regardless if I didn't know about the renix harness. I was assuming from your post you had an 98 xj. Then you posted your info. Let us know how you are making out ok?
11-02-2017, 09:27 AM
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Hey cruiser54.
I did slap a multimeter onto the wiring while the torx screws were loose on the TPS, got the voltage, did the math, and made sure the TPS was adjusted until it read 17%, then locked it down.
I replaced the rotar, distirbuter cap, spark plug wires,and spark plugs as well.
Cruiser, are the harnesses as simple as plug and play when replacing? They definitely need replacing...
Didnt go as in depth as your tips suggest, so ill jump on it and get back to you.
Oh, and thanks 97grand4.0. Hope I didnt come across as snarky, I appreciate the quick responses.
I did slap a multimeter onto the wiring while the torx screws were loose on the TPS, got the voltage, did the math, and made sure the TPS was adjusted until it read 17%, then locked it down.
I replaced the rotar, distirbuter cap, spark plug wires,and spark plugs as well.
Cruiser, are the harnesses as simple as plug and play when replacing? They definitely need replacing...
Didnt go as in depth as your tips suggest, so ill jump on it and get back to you.
Oh, and thanks 97grand4.0. Hope I didnt come across as snarky, I appreciate the quick responses.
I think you're gonna find a few things as you go along. Ground path for the sensors is bad and/or TPS is bad.
The symptoms point to those things. A vacuum leak, while always good to look for, would not cause a high idle and then have it die down.
Last edited by cruiser54; 11-02-2017 at 09:30 AM.
11-08-2017, 01:26 AM
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SO!
After hitting tips 1, 3, 4, & 5 on Cruizer's website (which are great btw), still no joy.
It takes a solid 3-5 minutes, from a cold start, of letting the vehicle crank before the engine will finally turn over. And still, from a cold start, the RPMs hover low. No stalling at stops or random engine cut offs (except once, from not securing an electrical connection completely after cleaning it during one of Cruizer's steps...).
What do you think ladies/gents? I know Cruizer, you mentioned it might be a bad TPS sensor, but popping a multimeter on the thing, Im receiving the correct voltage (17% of 5volts ~ .84) so I am not too sure. IAC is brand new, TB is clean, new gasket there as well, new air filter...
I did notice that a few of the electrical pigtails on the fuel injectors do not have the metal bracket on the electrical connector (so you can essentially pull them straight off). But they are all secure and do not wiggle freely of there own accord. So not sure if that has anything to do with this.
With not prior knowledge of cars in general, this seems like a fuel pressure issue. Like the engine may not be getting enough fuel to support combustion until initially? And needs a bit for the fuel to air ratio to hit that sweet LEL spot? Could it possibly the Fuel Filter being old and there for partially clogged which is bogging down the fuel delivery to the fuel pressure regulator and subsequent fuel injectors? Or even the fuel pump not pushing as much as needed? There is a rather loud audible kick on of the fuel pump once I turn the key...
After hitting tips 1, 3, 4, & 5 on Cruizer's website (which are great btw), still no joy.
It takes a solid 3-5 minutes, from a cold start, of letting the vehicle crank before the engine will finally turn over. And still, from a cold start, the RPMs hover low. No stalling at stops or random engine cut offs (except once, from not securing an electrical connection completely after cleaning it during one of Cruizer's steps...).
What do you think ladies/gents? I know Cruizer, you mentioned it might be a bad TPS sensor, but popping a multimeter on the thing, Im receiving the correct voltage (17% of 5volts ~ .84) so I am not too sure. IAC is brand new, TB is clean, new gasket there as well, new air filter...
I did notice that a few of the electrical pigtails on the fuel injectors do not have the metal bracket on the electrical connector (so you can essentially pull them straight off). But they are all secure and do not wiggle freely of there own accord. So not sure if that has anything to do with this.
With not prior knowledge of cars in general, this seems like a fuel pressure issue. Like the engine may not be getting enough fuel to support combustion until initially? And needs a bit for the fuel to air ratio to hit that sweet LEL spot? Could it possibly the Fuel Filter being old and there for partially clogged which is bogging down the fuel delivery to the fuel pressure regulator and subsequent fuel injectors? Or even the fuel pump not pushing as much as needed? There is a rather loud audible kick on of the fuel pump once I turn the key...
11-08-2017, 05:37 AM
#13
CF Veteran
Fuel is a necessity, obviously. I just spent a day troubleshooting my son's gas dryer, only to find he had shut off the gas.
So I suggest a fuel pressure tester here and follow the procedure for your year make and model.
So I suggest a fuel pressure tester here and follow the procedure for your year make and model.
11-08-2017, 06:56 AM
#14
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Year: 1990
Model: Cherokee (XJ)
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SO!
After hitting tips 1, 3, 4, & 5 on Cruizer's website (which are great btw), still no joy.
It takes a solid 3-5 minutes, from a cold start, of letting the vehicle crank before the engine will finally turn over. And still, from a cold start, the RPMs hover low. No stalling at stops or random engine cut offs (except once, from not securing an electrical connection completely after cleaning it during one of Cruizer's steps...).
What do you think ladies/gents? I know Cruizer, you mentioned it might be a bad TPS sensor, but popping a multimeter on the thing, Im receiving the correct voltage (17% of 5volts ~ .84) so I am not too sure. IAC is brand new, TB is clean, new gasket there as well, new air filter...
I did notice that a few of the electrical pigtails on the fuel injectors do not have the metal bracket on the electrical connector (so you can essentially pull them straight off). But they are all secure and do not wiggle freely of there own accord. So not sure if that has anything to do with this.
With not prior knowledge of cars in general, this seems like a fuel pressure issue. Like the engine may not be getting enough fuel to support combustion until initially? And needs a bit for the fuel to air ratio to hit that sweet LEL spot? Could it possibly the Fuel Filter being old and there for partially clogged which is bogging down the fuel delivery to the fuel pressure regulator and subsequent fuel injectors? Or even the fuel pump not pushing as much as needed? There is a rather loud audible kick on of the fuel pump once I turn the key...
After hitting tips 1, 3, 4, & 5 on Cruizer's website (which are great btw), still no joy.
It takes a solid 3-5 minutes, from a cold start, of letting the vehicle crank before the engine will finally turn over. And still, from a cold start, the RPMs hover low. No stalling at stops or random engine cut offs (except once, from not securing an electrical connection completely after cleaning it during one of Cruizer's steps...).
What do you think ladies/gents? I know Cruizer, you mentioned it might be a bad TPS sensor, but popping a multimeter on the thing, Im receiving the correct voltage (17% of 5volts ~ .84) so I am not too sure. IAC is brand new, TB is clean, new gasket there as well, new air filter...
I did notice that a few of the electrical pigtails on the fuel injectors do not have the metal bracket on the electrical connector (so you can essentially pull them straight off). But they are all secure and do not wiggle freely of there own accord. So not sure if that has anything to do with this.
With not prior knowledge of cars in general, this seems like a fuel pressure issue. Like the engine may not be getting enough fuel to support combustion until initially? And needs a bit for the fuel to air ratio to hit that sweet LEL spot? Could it possibly the Fuel Filter being old and there for partially clogged which is bogging down the fuel delivery to the fuel pressure regulator and subsequent fuel injectors? Or even the fuel pump not pushing as much as needed? There is a rather loud audible kick on of the fuel pump once I turn the key...
What happens if you cycle the key On and Off about 3 times before going to Start?
11-08-2017, 07:18 AM
#15
CF Veteran
Another thought, I just had a similar thing with my 98xj which sat for quite a while...would crank and crank then slowly start...turned out the idle air control was sticking...a shot of carb cleaner seemed to do the trick and now it's back to it's old self ..starts right up.